1,720,977 research outputs found
An Efficient Algorithm for the Computation of the UTD Transition Function
No full textWe present an efficient algorithm for the numerical
calculation of the canonical transition function, which is encountered
in the uniform geometrical theory of diffraction (UTD).
Such a transition function allows the uniform ray field description
of various high-frequency diffraction mechanisms, such as double
wedge or vertex diffraction. The proposed algorithm is valid for
both real and imaginary arguments as required to deal with the
general case in UTD applications
A UTD Triple Diffraction Coefficient for Straight Wedges in Arbitrary Configuration
No full textAnew UTD solution is presented for the description of
the ray triply diffracted by straight wedges in arbitrary configuration,
illuminated by a spherical wavefront field. The proposed UTD
coefficient permits to uniformly describe the field at any aspect,
in particular including the case of overlapping transition regions,
where the subsequent application of UTD single wedge diffraction
coefficient fails. The triple diffracted ray field is expressed in an analytical
form, providing physical insight into the triple diffraction
mechanism, and a new effective engineering tool within the UTD
framework, as required in a modern ray-based code
UHF and L-Band Microwave Measurements of the Antarctic Firn-Layer Complex Permittivity Depth Profile
No full textIn order to characterize the complex permittivity depth profile of the firn constituting the Antarctic ice sheet, a microwave probe, based on the open-coaxial re-entrant cavity method, is designed, realized and then used during an Antarctic campaign. Preliminary results of the measurements of firn permittivity depth profile, are presented and discussed highlighting very good agreement with expected values
Algorithm for the Computation of the Generalized Fresnel Integral
No full textThe generalized Fresnel Integral appears as a canonical function in the uniform ray field representation of several high-frequency diffraction mechanisms, such as double wedge or vertex diffraction. Here we propose an algorithm for its calculation which is valid both for real and imaginary arguments as required for treating the general case in the uniform geometrical theory of diffraction framework
Degrees of Freedom of the Field as the Upper Bound for the Number of MIMO Independent Channels
No full textWireless communication systems have rapidly evolved, becoming a driving force behind the global digital transformation. This has fostered connectivity and enabled the seamless exchange of information. Electromagnetic Information Theory (EMIT) represents a theoretical framework that explores the fundamental principles governing the transmission and reception of information through electromagnetic waves. Indeed, in wireless communication systems, the electromagnetic field acts as a medium for information transfer. EMIT has therefore emerged as a transformative paradigm, promising to redefine the landscape of next-generation wireless communication. At its core, the concept of Degrees of Freedom (DoF) of the electromagnetic field refers to the inherent capacity of the field to assume multiple independent configurations, allowing for the simultaneous transmission of diverse information streams. This capacity for simultaneous transmission is crucial in the context of next-generation wireless communication, where the demand for higher data rates, lower latency, and increased reliability is ever-growing. The DoF of the field can be harnessed to create multiple independent channels, each capable of carrying distinct information payloads. By understanding and manipulating these DoF, researchers and engineers can optimize the utilization of the electromagnetic spectrum, overcoming the limitations posed by traditional communication systems
Modeling and dielectric characterization of EMI/EMC ground test for the evaluation of the electric propulsion thruster emissions
No full textA new EMI test facility for electric propulsion (EP) thrusters has been developed at Aerospazio Tecnologie. The facility consists of a cylindrical dielectric vacuum tank placed in a semi-Anechoic room, connected through a gate valve to a Large Vacuum Test Facility. The electromagnetic characterisation of the facility, along with subsequent measures of the radiated emissions of a Hall effect thruster, is presented
An Open-Resonator Sensor for Measuring the Dielectric Properties of Antarctic Ice
Full text linkIn this paper, the theory behind the design of a microwave sensor for the accurate measurement of firn complex permittivity is presented. This class of microwave sensors, based on the open-coaxial re-entrant cavity method, is specifically designed to measure, by means of a simple and quick procedure, the complex permittivity profile of low loss materials. A calibration procedure is introduced to derive the complex permittivity of the material under measurement (MUM). Two specimens of this class of microwave sensors have been realized to sample the complex permittivity profile of a 106-m long ice core drilled from the Antarctic plateau at Concordia Station. The preliminary results of the on site measurement campaign are reported, showing very good agreement with theoretical models available in the literature
Permittivity depth profile measurements of the antarctic firn layer in the 0.4-2 GHz band
No full textA microwave sensor aimed to characterize the complex permittivity depth profile of the Antarctic firn layer is presented. It is based on the open-coaxial re-entrant cavity method. Preliminary results of the measured permittivity depth profile on the Antarctic firn is also presented showing a very good agreement to expected values
High-frequency characterization of EMI/EMC ground test facility for the measurements of electric propulsion thruster emissions
No full textIn this paper an electromagnetic characterization of an EMI/EMC test facility for electric propulsion thrusters is presented. The facility consists of a dielectric vacuum chamber placed in a semi-anechoic room and connected to a Large Vacuum Test Facility. To this end, an analysis of the electromagnetic field radiated outside a canonical infinite dielectric cylinder by an internal line source has been conducted. First the two-dimensional Green's Function for the electromagnetic radiation by a line source inside the canonical dielectric hollow cylinder is developed. Then, two high frequency emission models based on Geometrical Optics and on an iterative implementation of the Physical Optics are formulated and the results compared to those of the Green's function method. The numerical results show very good agreement between the simplified high frequency techniques and the exact formulation
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